How to Install Nagios

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Installation

yum install php httpd mysql gd gd-devel gcc glibc glibc-common nagios nagios-plugins-all nagios-plugins-nrpe nrpe
service mysqld start
change the root password    #Just in case
service mysqld stop
edit the firewall to allow port 80 from everywhere 
vim /etc/nagios/objects/contacts.cfg => Change the email to your email
vim /etc/httpd/conf.d/nagios.conf
Comment out the lines “Order allow,deny” and “Allow from all” and add these lines: Order deny,allow Deny from all Allow from 127.0.0.1 169.230.26.0/24 169.230.90.0/24 10.20.0.0/16
htpasswd /etc/nagios/passwd nagiosadmin service nagios start service httpd start chkconfig nagios on chkconfig httpd on

CONFIGURE NAGIOS/ADDING CLIENTS:

http://nagios.sourceforge.net/docs/3_0/macrolist.html
http://nagios.sourceforge.net/docs/3_0/monitoring-publicservices.html
http://wiki.centos.org/HowTos/Nagios 

Plugins list: https://nagios-plugins.org/doc/man/index.html To see how a specific plugin works (say for ssh):

/usr/lib64/nagios/plugins/check_ssh --help 

The different timeperiods are defined here:

/etc/nagios/objects/timeperiods.cfg

Dummy templates for setting up dummy client.cfg files are here:

/etc/nagios/objects/templates.cfg 

To add a client:

ssh to the client and do the following:
yum install nrpe nagios-plugins-all openssl
vim /etc/nagios/nrpe.cfg  => Changed: 
 allowed_hosts=169.230.26.197 (the ip of the nagios server)
service nrpe start
chkconfig nrpe on 
              • NOTE FOR CENTOS 5*****************

For i386:

rpm -Uvh http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS//rpmforge-release-0.5.3-1.el5.rf.i386.rpm

For x86_64:

rpm -Uhv http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS//rpmforge-release-0.3.6-1.el5.rf.x86_64.rpm

Back on nagios server:

vim /etc/nagios/nagios.cfg
Uncomment this line   =>      cfg_dir=/etc/nagios/servers
mkdir /etc/nagios/servers
vim /etc/nagios/servers/client_hostname.cfg

I created one that looks like this for delta.cfg: ++++++++++++++++++++++++++++++++++++++++++++

define host{
       use                             linux-server
       host_name                       delta.cluster.ucsf.bkslab.org
       alias                           delta
       address                         10.20.1.4
       max_check_attempts              5
       check_period                    24x7
       notification_interval           30
       notification_period             24x7
} 
define service { use generic-service host_name delta.cluster.ucsf.bkslab.org service_description PING check_command check_ping!100.0,20%!500.0,60% } define service { use generic-service host_name delta.cluster.ucsf.bkslab.org service_description SSH check_command check_ssh notifications_enabled 1 } define service { use generic-service host_name delta.cluster.ucsf.bkslab.org service_description Current Load check_command check_local_load!5.0,4.0,3.0!10.0,6.0,4.0 }

+++++++++++++++++++++++++++++++++++

service nagios restart

That’s pretty much it! Nagios Hostgroups:

On the nagios server: vim /etc/nagios/nagios.cfg Add the line => cfg_file=/etc/nagios/objects/hostgroups.cfg vim /etc/nagios/objects/hostgroups.cfg => define hostgroup{

       hostgroup_name  cluster_2

}

Then to add a server to this hostgroup: vim /etc/nagios/servers/delta.cfg Add this line within the “define host” curly brackets => hostgroups cluster_2

service nagios restart


References:

http://www.unixmen.com/install-and-configure-nagios-in-centos-6-4-rhel-6-4/ https://www.digitalocean.com/community/tutorials/how-to-install-nagios-on-centos-6